Method of controlling an inverter during MOSFET shorts

Abstract

Technical solutions are described for mitigating braking torque in a motor of a steering system caused by a FET short. For example, an example mitigation system includes a mitigation module that adjusts a motor torque in response to a FET short. The mitigation system further includes a mitigation-enable module that selectively enables and disables the mitigation module based on a handwheel torque signal. Further, the mitigation system includes a damping module that reduces the motor torque based on a motor velocity signal for the motor.

What is claimed is: 
     
       1. A system for mitigating braking torque in a motor of a steering system, the system comprising:
 a mitigation module that adjusts a motor torque in response to a FET short; 
 a mitigation-enable module that selectively enables and disables the mitigation module based on a handwheel torque signal; and 
 a damping module that reduces the motor torque based on a motor velocity signal for the motor. 
 
     
     
       2. The system of  claim 1 , wherein the mitigation-enable module enables the mitigation module in response to the handwheel torque signal being above a predetermined threshold. 
     
     
       3. The system of  claim 2 , wherein the mitigation-enable module disables the mitigation module in response to the handwheel torque signal being at or below the predetermined threshold. 
     
     
       4. The system of  claim 1 , wherein the handwheel torque signal is indicative of input torque to the steering system in response to the FET short. 
     
     
       5. The system of  claim 1 , wherein the mitigation module determines a scaling factor for a modulation index used during mitigation of the FET short. 
     
     
       6. The system of  claim 1 , wherein the damping module includes a low pass filter that generates filtered motor velocity prior to determining a damping-factor to reduce the motor torque. 
     
     
       7. The system of  claim 1 , wherein the damping module is configured to reduce a braking torque component included in the motor torque according to a back electro-magnetic field of the motor. 
     
     
       8. The system of  claim 7 , wherein the back electro-magnetic field is proportional to the motor velocity. 
     
     
       9. A method for mitigating braking torque in a motor, the method comprising:
 adjusting, by a mitigation module, a motor torque generated by the motor in response to a FET short; 
 selectively enabling and disabling, by a mitigation-enable module, the mitigation module based on an input torque signal; and 
 reducing, by a damping module, the motor torque based on a motor velocity signal for the motor. 
 
     
     
       10. The method of  claim 9 , further comprising enabling the mitigation module, by the mitigation-enable module, in response to the input torque signal being above a predetermined threshold. 
     
     
       11. The method of  claim 10 , further comprising disabling the mitigation module, by the mitigation-enable module, in response to the input torque signal being at or below the predetermined threshold. 
     
     
       12. The method of  claim 9 , wherein the input torque is indicative of a torque generated by the motor in a previous iteration. 
     
     
       13. The method of  claim 9 , further comprising determining, by the mitigation module, a scaling factor for a modulation index used during mitigation of the FET short. 
     
     
       14. The method of  claim 9 , further comprising filtering, by the damping module, using a low pass filter, the motor velocity prior to determining a damping-factor to reduce the motor torque. 
     
     
       15. The method of  claim 9 , further comprising reducing, by the damping module, a braking torque component included in the motor torque according to a back electro-magnetic field of the motor. 
     
     
       16. The method of  claim 15 , wherein the back electro-magnetic field is proportional to the motor velocity. 
     
     
       17. A computer program product comprising a non-volatile computer readable storage medium, the computer readable storage medium comprising computer executable instructions, wherein the computer readable storage medium comprises instructions to:
 adjust, by a mitigation module, a motor torque generated by the motor in response to a FET short, the motor torque being generated to assist an input torque; 
 selectively enable and disable the mitigation module based on the input torque; and 
 reduce the motor torque based on a motor velocity signal for the motor. 
 
     
     
       18. The computer program product of  claim 17 , further comprising instructions to enable the mitigating in response to the input torque being above a predetermined threshold. 
     
     
       19. The computer program product of  claim 18 , further comprising instructions to disable the mitigating in response to the input torque being at or below the predetermined threshold. 
     
     
       20. The computer program product of  claim 17 , wherein reducing the motor torque comprises: reducing a braking torque component included in the motor torque according to a back electro-magnetic field of the motor, the back electro-magnetic field being proportional to the motor velocity.